Adjustable force powerized stapler

ABSTRACT

A powerized stapler device is disclosed including an electromagnet, preferably a solenoid, having a armature which is adjustable relative to the solenoid such that the permeable portions of the armature, in the non-energized condition of the solenoid, may be adjusted relative to the solenoid enabling the force exerted by the solenoid to be varied as a function of the initial position of the armature. In a further preferred embodiment, an extension of the armature is engaged with the stapler head whereby movements of the armature relative to the electromagnet also function to vary the space between the stapler head and the stapler anvil, adjustments to process thin work pieces functioning to reduce the spacing between stapler head and anvil as well as reducing the driving force exerted by the electromagnet. In a preferred embodiment, a sensor mechanism is provided which mechanically urges the stapler head toward or away from the anvil and shifts the position of the armature into or out of the core of a solenoid in accordance with the thickness of the work piece as sensed by the sensor mechanism.

BACKGROUND AND FIELD OF THE INVENTION

The present invention is directed to a powerized stapler device and moreparticularly to a stapler device wherein the driving force imparted tothe head of the stapler may be varied within a wide range such that agreater driving force is applied when a multiplicity of sheets are to bestapled and conversely, a lower driving force is applied where thestaple is to be clinched through a limited number of sheets.

1. Prior Art

Powerized stapling devices have been available for many years,representative examples being disclosed in U.S. Pat. Nos. 2,403,947;2,877,461; 2,957,174; 2,975,424; 3,016,538; 3,022,512; 3,026,518;3,101,478; 3,151,329; 3,251,524, assigned to the assignee hereof. Thereferences noted disclose, in general, staplers integrated into ahousing, carrying an electromagnetic mechanism such as a solenoid, thearmature of the solenoid being disposed above the drive head of thestapler. Insertion of articles to be stapled activates a switchmechanism energizing the solenoid and causing the armature to drive thestapler through an operating cycle

A difficulty inhering in staplers of the type described resides in thefact that the stapling force imparted is identical for stapling jobsconsisting of a multiplicity of sheets and also for jobs involving onlya few sheets. Where the applied force is sufficient for joining multiplesheets and the same force is utilized in joining jobs comprised of onlya few sheets, one or the other of the jobs will be defective. Moreparticularly, if the force is insufficient to drive a staple through amultiple sheet job, an effective clinching will not result. Conversely,if a force sufficient for multiple sheet stapling is utilized inconnection with a two or three sheet job, the stapler will act in themanner of a punch, the base of the overdriven staple penetrating one ormore of the sheets whereby the upper most ones of the sheets are noteffectively connected to the remainder of the sheets.

A further problem inhering in the application of overly great staplingforces when connecting a limited number of sheets, resides in theexcessive impact leaving an imprint surrounding the area of stapleapplication.

A still further drawback of known powerized staplers, particularly whenused to fasten a limited number of sheets, resides in the staple beingapplied with a rolling or angular clinch. The rolling clinch resultsfrom the fact that the sheets are moving a finite distance after thesensor, which activates the stapler, is energized. As a result, the legsof the staple penetrate the sheets while the sheets are still moving,whereby the base of the staple has passed a slight distance beyond theclinching anvil, resulting in a rolling or loosely applied staple. Thedescribed problem is of lesser significance where a multiplicity ofsheets are to be stapled since the multiple sheets act as a support forthe staple as it is driven. Additionally, the thickness of the multiplesheets assures that impact between the stapler head and the upper mostsheet occurs promptly following energizing of the power mechanism sincethe upper most sheet of a thick stack will be closer to the stapler headthan would be the case where only a few sheets are to be connected.

Various means have been proposed to provide stapling devices wherein thedriving power may be adjusted. These known devices utilize electroniccircuitry for varying the voltage applied to the solenoid or otherelectromagnetic driving means. While these devices enable the user totailor the driving force, within a limited range, to the job at hand,they do not solve the problems discussed above, and particularly theproblem of avoiding a rolling staple connection when used to join alimited number of sheets.

A further drawback of known powerized staplers resides in the fact thatthe power must be manually adjusted in accordance with the job at hand.Thus, where the user will sequentially staple thin and thick stacks ofarticles, adjustment must be manually effected between each application,greatly slowing the stapling procedure. Additionally, manual adjustmentinvolves discretion on the part of the user and thus is a minimal aid tothe occasional powerized stapler user.

SUMMARY OF THE INVENTION

The present invention may be summarized as directed to an improvedpowerized stapling device characterized in that a unique means isemployed for varying the force of the stapling stroke, enabling a moreprecise and wider range of stapling force than is available to powerizedstaplers utilizing electronic adjustment of stapling force.

The invention is further directed to a variable power-stapling device,which automatically adjusts stapling force to the thickness of thearticles to be stapled.

A still further object of the invention resides in the provision of avariable power stapler wherein adjustment of the stapling forcefunctions, in addition, to vary the spacing between the stapler head andthe upper most of the stack of sheets to be stapled. More particularly,adjustment of the stapling force to reduce the force also functions toshift the stapler drive head closer to the upper most sheet whereby thetime lag between energization and actual driving of a staple is reduced.Conversely, where a large number of sheets are to be connectedadjustment of the driving force to increase the same also results inmoving the stapler head further from the upper most of the thick stackof articles maximizing inertia applied to the stapler.

The invention is further directed a unique means for varying thestapling force thereby eliminating the use of electronic controls. Knownelectronic controls, namely voltage reducers do not function below athreshold voltage eliminating the desired “soft touch” where a limitednumber of sheets or poly bags are to be stapled. More specifically,adjustment of stapling power in accordance with the invention isaccomplished by providing an electromagnetic drive mechanism andparticularly a solenoid which includes an armature incorporating a highpermeability portion, adjustment of the stapling force being effected byshifting the position of the high permeability portion relative to thecore of the solenoid. For example, where the major portion of the highpermeability material is positioned such that it will be drawn into thesolenoid upon energization, a greater force is applied to the armaturethan is the case is where a majority of the high permeability materialis already located within the solenoid.

It is an object of the invention to provide a force adjustable staplingdevice wherein adjustment of the driving force is accompanied by aconcomitant movement of the stapler head toward and away from the work.

A further object of the invention is the provision of a variable forcestapling device, wherein the driving force is automatically variedresponsive to the thickness of the stack of articles to be stapled.

A still further object of the invention is the provision of a means forvarying the force applied in a stapling operation by varying theposition of an armature with respect to an electromagnetic mechanismoperatively coupled to the armature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a stapler in accordance with theinvention.

FIGS. 2a and 2 b are cross-sectional views of improperly driven staplesas effected using prior art powerized stapling devices.

FIG. 3 is magnified cross-sectional view taken on the line 3—3 of FIG.1.

FIG. 4 is an exploded pre-assembly view of the driving mechanism of thestapler.

FIGS. 5 and 7 are vertical sectional views showing the relativepositions of the driver mechanism adjusted respectively for connecting alimited number of sheets and larger number of sheets.

FIGS. 6 and 8 are sectional views respectively illustrating a stapleclinched by the device adjusted per FIG. 5 and the device adjusted perFIG. 7.

FIG. 9 is a vertical cross-section of an embodiment of the inventionincorporating an automatic thickness adjustment.

FIG. 10 is an exploded perspective view of the embodiment of FIG. 9.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to FIG. 1, a force adjustable stapler 10 includes ahousing 11 having a base 12 on which is mounted a conventional stapler13. An adjustment knob 14 carries a microswitch or like trip mechanism(not shown) fixed to the knob 14 enabling the user to adjust the spacingfrom the edge of the work at which the staple will be applied.

In the embodiment of FIG. 1 the force with which a staple is applied iscontrolled by force adjustment dial 15.

Details of the force adjustment mechanism are best appreciated from aninspection of FIGS. 3 and 4. The stapler 13 includes a drive head 16carrying on its upper surface a buffer 17 of felt or elastomer. The head16 of the stapler is biased upwardly by conventional means such asreturn spring 18.

Driving power is provided by an electromagnetic assembly, illustrativelysolenoid 19. Solenoid 19 includes a housing 20 which includes agenerally U-shaped mounting bracket 21 including in-turned legs 22,23(FIG. 4). The legs 22,23 are provided with threaded apertures 24, thebracket 21 being mounted to the side wall 25 of the housing by machinescrews 26 passing through apertures 27 in side wall 25 and threaded intothe apertures 24 of the bracket 21.

An L-shaped bracket 28 forms a support for the adjustment assembly, thebracket including a vertically directed leg 29 fixed to sidewall 25 ofthe housing by machine screws 30 passing through apertures 31 in theside wall and extending into complementary threaded apertures 32 in themember 29.

The solenoid 19 includes an armature assembly 33, the assembly beingcomprised of two components, namely an upper component 34 formed of ahigh permeability magnetic material such as soft iron and a lowercomponent 35 formed of a low permeability or non-magnetic material suchas brass. The armature assembly 33 is vertically movable within the core36 of the solenoid. Force variation is a function of the position of thehigh permeability material 34 relative to the core 36 of the solenoid.

More particularly, when the high permeability component 34 is onlypartially disposed within the core 36 (FIG. 7 and solid line position ofdial 15, see FIG. 3) energization of the solenoid 19 will draw the highpermeability component downwardly until essentially the entirety of thecomponent 34 enters the core 36. When the component 34 is adjusteddownwardly to the position of FIG. 5 and the dot and dash position (FIG.3) in a manner hereinafter described, the element 34 will movedownwardly upon energization of the solenoid 19, only a relatively smalladditional distance, i.e. until the balance of the high permeabilitycomponent in introduced into the core 36.

The mechanism for adjusting the relative position of the highpermeability portion 34 relative to core 36, i.e. the force adjustmentmechanism will next be described.

Bracket 28 includes a generally horizontally directed leg 37 havingformed therein a threaded aperture 38. An adjustment rod 39 includes athreaded lower portion 40 threadedly mounted in aperture 38. A circularflange 41 is welded as at 42 to the rod 39, coil spring 43 being biasedbetween the leg 37 and flange 41.

Force adjustment knob 15 is keyed to rod 39 as by set screw 44.

The adjustment rod 39 carries a thrust cap 45 at the lower end of therod, the base 46 of the cap bearing against pad 47 bonded to the uppersurface 48 of the high permeability portion 34 of the armature assembly33. The pad 48 is preferably formed of a somewhat compressible materialsuch as a heavy felt, neoprene or like elastomer.

As will be apparent from the preceding description, by rotating theforce adjustment dial 15 in a manner to thread rod 39 in a downwarddirection (see dot and dash condition FIG. 3) two complementaryfunctions, each of which reduce the driving force of the stapler, aresimultaneously effected.

More particularly, increments of the high permeability portion 34 ofarmature assembly 33 are introduced into the solenoid coil and at thesame time, the inert component 35 of the armature assembly forces pad 17downwardly moving the stapler head 16 closer to the anvil 50 of thestapler.

As will be appreciated, upon energization of the solenoid 19 thearmature assembly 33 will always move to a predetermined lowermostposition. However, the force imparted to the stapler head will vary froma maximum force wherein virtually the entirety of the high permeabilitycomponent 34 is drawn into the solenoid to a minimum force wherein themajority of the high permeability portion is already situated within thecore 36 of the solenoid.

The described force adjustment mechanism has the further advantage,where minimal force is desired, as for connecting a limited number ofsheets, of bringing the head of the stapler close to the anvil wherebythe time lag between penetration and clinching of a staple which passesthrough only a few sheets is minimized.

In FIG. 2a there is illustrated a staple S which has been applied withunduly high force. As is apparent, the staple legs are curved upwardlyand the staple ends may penetrate the uppermost surface of the workproviding minimal support for the lowermost sheet, the uppermost portionof the staple often being forced through the uppermost sheet.

In FIG. 2b there is illustrated the rolling effect which results fromstaple S′ being applied while the work piece is still moving afterenergizing of the switch mechanism triggering a stapling cycle. Therolling or angular configuration assumed by the staple relative to thework piece is a result of the relatively long time lag resulting fromthe fact that the stapler head must move through a large arc beforeclamping the work piece, where only a few sheets are to be processed.This results in a staple in which spaces are formed between the back ofthe staple and the work on the top surface and between the legs and theunder surface as shown.

Referring to FIG. 5, the device has been adjusted to process a limitednumber of layers L. In this adjusted position it will be observed thatthe distance D between the stapler head and anvil 50 is smaller than thedistance D′ (FIG. 7) where the device has been adjusted to apply maximumforce. The relative positions of the parts may also be appreciated bynoting the close spacing of the arrows 5—5 in FIG. 5 and the greaterspacing of the arrows 7—7 of FIG. 7.

FIGS. 6 and 8 illustrate the ideal clinching obtained by utilizing theadjustments provided by FIGS. 5 and 7 respectively.

In FIGS. 9 and 10 there is illustrated an embodiment of the inventionwhich provides automatic adjustment of the applied force in accordancewith the thickness of the work to be stapled

Referring now to FIGS. 9 and 10, force adjustment previously effected byadjustment of the control knob 15 is automatically accomplished inaccordance with the thickness of the work to be stapled by an automaticadjustment mechanism referred to generally by reference numeral 60. Thesolenoid 19 and armature assembly 33 are essentially identical to thedevice of the previously described embodiment. The housing front wall 61includes an extension 62 to the side wall 63 on which is rotatablymounted an adjustment shaft 64. The shaft 64 carries a pinion gear 65which meshes with rack 66 guided for vertical movement by rack supportbrackets 67,68 bolted to housing wall 61. The rack includes a drive arm69 superposed over the high permeability component 34 of the armatureassembly 33.

Drive nut 70 is clamped to arm 69 as by machine screw 71, the lowersurface of the drive nut being in contact with buffer pad 47 fixed tothe armature component 34.

The shaft 64 includes an offset lever arm 72 on which is mounted asensor roller 73 horizontally disposed in the path of the work W to bestapled. As is apparent from FIGS. 9 and 10, the work piece W wheninserted past the sensor roller 73 will cause the shaft 64 to rotate ina clockwise direction lifting rack 66. Contact between the pad 17 andthe undersurface of the non-permeable armature component 34 ismaintained by the upward springing force provided by spring 18 of thestapler.

As will be apparent by comparing the solid and dot and dash positions ofthe components as shown in FIG. 9, the thicker the work piece W thegreater the rotation of the pinion gear 65 and concomitantly the greaterthe spacing the stapler from anvil 50. Similarly, the high permeabilityportion 34 will be withdrawn from the core of the solenoid 19 providingmaximum driving force and travel of the armature assembly within thesolenoid core.

As will be apparent, insertion of a thin work piece will shift roller 73only slightly in a clockwise condition permitting the stapler head toshift only slight distance upwardly whereby the major mass of the highpermeability component will remain within the solenoid providing arelatively short stroke of the armature assembly when the solenoid isenergized.

It will thus be recognized that the automatic adjustment assemblydescribed controls both the spacing of the stapler from the work pieceand also the force generated by the electromagnetic device uponenergizing the coil 19.

From the foregoing, it will be appreciated that there is described inaccordance with the invention a powerized stapler device characterizedin that the force with which a staple is driven may be accuratelycontrolled, whereby greater forces are applied where a thick work pieceis processed than is the case where the work piece is comprised of onlya few sheets or, a readily deformed material such as a polyethylene bag.

A further characterizing feature of the invention resides in the devicecontrolling both the force generated by the electromagnetic drivemechanism and also by a shifting of position of the stapler head towardand away from the work piece in accordance with the desired staplingresult.

A further feature of the invention resides in mechanically controllingthe force exerted by the electromagnetic drive mechanism as a functionof the adjusted position of the high permeability component of thearmature mechanism relative to the electromagnetic device.

A still further characterizing feature of the invention resides in adevice which automatically senses the thickness of the work load to bestapled and accordingly adjusts both the position of the stapler headand the force with which the stapler is driven.

As will be apparent to those skilled in the art and familiarized withthe instant disclosure numerous variations in structural details may bemade without departing from the spirit of the invention. Accordingly,the invention is to be broadly construed within scope of the appendedclaims.

I/we claim:
 1. A variable force powerized stapler assembly comprising ahousing having a base, a stapler mounted on said base including a drivehead shiftable toward and away from said base, drive means including anelectromagnet mounted on said housing for actuating said stapler throughan operative cycle, said drive means including an armature assemblyhaving a high permeability portion and an extension engaging said drivehead and adjustment means operatively associated with said armatureassembly, said adjustment means including sensor means on said baseresponsive to the thickness of articles to be stapled for shifting theposition of said high permeability portion relative to saidelectromagnet to thereby vary the force imparted to said armature uponenergization of said electromagnet responsive to the sensed thickness ofsaid articles.
 2. Apparatus in accordance with claim 1, wherein saidsensor means comprises a lever fixed to said housing and pivotallymovable about a horizontal axis, an abutment on said lever positioned inthe path of articles advanced beneath said drive head and coupling meansinterposed between said lever and said armature assembly for shiftingsaid armature assembly toward and away from said base in accordance withthe extent of pivotal movement of said lever.
 3. Apparatus in accordancewith claim 2, wherein said coupling means comprises a pinion mounted onsaid lever and a rack meshed with said pinion.
 4. Apparatus inaccordance with claim 1, wherein said electromagnet comprises a solenoidhaving a core and said armature assembly is axially movably mountedwithin said core.
 5. Apparatus in accordance with claim 1, wherein saiddrive head of said stapler is shifted toward and away from said base inaccordance with the adjusted position of said armature assembly relativeto said electromagnet.
 6. A variable force powerized stapler assemblycomprising a housing having a base, a stapler mounted on said baseincluding a drivehead shiftable toward and away from said base, drivemeans including an electromagnet mounted on said housing for actuatingsaid stapler through an operative cycle, said drive means including anarmature assembly having a high permeability portion and an extensionengaging said drivehead, and adjustment means operatively associatedwith said armature assembly, said adjustment means including sensormeans on said base responsive to the thickness of articles to be stapledfor shifting said high permeability portion and said drivehead towardand away from said base in accordance with the position of saidadjustment means to thereby vary the force imparted to said stapler headupon energization of said electromagnet.
 7. Apparatus in accordance withclaim 6, wherein said sensor means comprises a lever mounted on saidhousing for pivotal movement about a horizontal axis, an abutment onsaid lever positioned in the path of articles advanced beneath saiddrive head and coupling means interposed between said lever and saidarmature assembly for shifting said armature assembly toward said basein accordance with the extent of pivotal movement of said lever. 8.Apparatus in accordance with claim 7, wherein said coupling meanscomprises a pinion mounted on said lever and a rack coupled to saidarmature assembly and meshed with said pinion.
 9. Apparatus inaccordance with claim 6, wherein said electromagnet comprises a solenoidhaving a core and said armature assembly is axially movable within saidcore.